Aroma deterioration is one of the biggest problems in processing tea beverages. The aroma of tea infusion deteriorates fast during heat sterilization and the presence of ferrous ion (Fe2+) aggravates it. The underlying mechanism remains unveiled. In this study, Fe2+was verified to deteriorate the aroma quality of green tea infusion with heat treatment. Catechins were necessary for Fe2+-mediated aroma deterioration. By enhancing the degradation of catechins, Fe2+dramatically increased the production of hydrogen peroxide (H2O2). Fe2+and H2O2together exacerbated the aroma of green tea infusion with heat treatment. GC-MS analysis revealed that the presence of Fe2+enhanced the loss of green/grassy volatiles and promoted the formation of new volatiles with diversified aroma characteristics, resulting in a dull scent of green tea infusion. Our results revealed how Fe2+induced aroma deterioration of green tea infusion with heat treatment and could help guide tea producers in attenuating the aroma deterioration of tea infusion during processing.Keywords:green tea infusion;aroma deterioration;ferrous ion;catechins;hydrogen peroxide
Submicroparticles are important components generally existed in chrysanthemum tea infusion, but their functionality, chemical composition, structure and self-assembly mechanism are unclear due to lack of suitable preparation method and research strategy. This study showed that submicroparticles promoted the intestinal absorption of phenolics in chrysanthemum tea infusion by comparison of chrysanthemum tea infusion, submicroparticles-free chrysanthemum tea infusion and submicroparticles. Submicroparticles efficiently prepared by ultrafiltration mainly consisting of polysaccharide and phenolics accounted for 22% of total soluble solids in chrysanthemum tea infusion. The polysaccharide, which was determined as esterified pectin with a spherical conformation, provided spherical skeleton to form submicroparticles. A total of 23 individual phenolic compounds were identified in submicroparticles with the total phenolic content of 7.63 μg/mL. The phenolics not only attached to the external region of spherical pectin by hydrogen bonds, but also got into hydrophobic cavities of spherical pectin and attached to the internal region by hydrophobic interactions.
The detection of heavy metals in tea infusions is important because of the potential health risks associated with their consumption. Existing highly sensitive detection methods pose challenges because they are complicated and time-consuming. In this study, we developed an innovative and simple method using Ag nanoparticles-modified resin (AgNPs-MR) for pre-enrichment prior to laser-induced breakdown spectroscopy for the simultaneous analysis of Cr (III), Cu (II), and Pb (II) in tea infusions. Signal enhancement using AgNPs-MR resulted in amplification with limits of detection of 0.22 μg L −1 for Cr (III), 0.33 μg L −1 for Cu (II), and 1.25 μg L −1 for Pb (II). Quantitative analyses of these ions in infusions of black tea from various brands yielded recoveries ranging from 83.3% to 114.5%. This method is effective as a direct and highly sensitive technique for precisely quantifying trace concentrations of heavy metals in tea infusions.
危险品化学品经营许可证（带存储）